Field of the Invention
The present invention relates to a procedure and system for harvesting bone graft material for use in skeletal bone fusion surgery, particularly in fusions of the spinal vertebrae.
Discussion of the Known Art
An object of spinal fusion surgery is to join adjacent vertebrae at an affected level of a patient's spine by inducing growth of solid bone tissue in the intervertebral disc space. The grown bone tissue acts to fuse the vertebrae together solidly and permanently. This procedure has long been known to reduce or eliminate severe back pain suffered by a patient when he or she assumes postures that cause the vertebrae at the affected level to move relative to one another in a certain manner.
See, e.g., my pending U.S. patent application Ser. No. 14/180,495 filed Feb. 14, 2014, titled Determining and Placing Spinal Implants or Prostheses, published as US 2014/0163573 (Jun. 12, 2014), and incorporated fully by reference.
In a typical fusion procedure, the disc space is cleaned and bone, or a bone-like graft material, is deposited in the space to promote the growth of bone tissue between the vertebrae and produce a healthy fusion. Among the available graft materials, bone graft harvested directly from the patient's own bone tissue (“autograft”) or from a donor, ceramics, bone morphogenic proteins, and/or stem cell based grafts are commonly used as bone growth stimulants. Of these, autograft obtained from the patient's iliac crest or pelvic area is known to work best to promote a successful fusion.
Using the patient's own bone tissue for graft material works well to form a confluence of the material with the vertebral bones to be fused. It is also known that (a) the more autograft material used, the greater the likelihood of achieving a successful fusion, and (b) a solid piece of autograft material works better than smaller chips to promote fusion. Basic principles of orthopaedic surgery suggest an optimum fusion will occur when a solid bone piece is inserted to span the entire intervertebral disc space, and when opposite ends of the piece enter or penetrate the end plates of the two vertebrae that face the disc space.
U.S. Pat. No. 7,201,775 (Apr. 10, 2007) discloses a procedure that calls for implanting a hollow cylindrical stabilizing device (see FIGS. 7 & 8 of the patent) between the end plates of two vertebrae to be fused, and rotating the device so that it gouges and shears off portions of the end plates, which portions are then forced inside of the device. The device has openings so that when oriented as in FIG. 11C of the patent, the bone portions inside the device are exposed to the vertebrae through the openings to promote a fusion, according to the patent. The procedure runs a risk of crushing the end plates and destroying the integrity of the remaining vertebral bone, however. That is, one or both vertebrae can become prone to fracture and compress into the spinal canal. Further, the device does not translocate or displace an intact piece of bone directly from one vertebra so as to enter the body of the other vertebra.
U.S. Pat. No. 8,328,870 (Dec. 11, 2012) describes an interbody fixation system including a cage having blades mounted inside the cage. When the blades are turned not more than about 45 degrees as shown in FIGS. 2 and 6C of the patent, the blades bite into the end plates of the opposed vertebrae and fix the position of the cage on and between the end plates, according to the patent. See also, U.S. Pat. No. 7,618,423 (Nov. 17, 2009) which relates to a system for performing spinal fusion including a graft holder assembly, a locking assembly, and a pair of bone graft implants that are introduced into a disc space to effect fusion; U.S. Pat. No. 8,353,912 (Jan. 15, 2013) disclosing an ultrasonic cleaning device for leveling the surfaces of the vertebral end plates after the disc space is cleaned and before graft material is deposited in the space, and U.S. Pat. No. 8,343,178 (Jan. 1, 2013) describing an ultrasonic saw blade for cutting hard bone without damaging adjacent soft tissue. All of the foregoing U.S. patents are fully incorporated by reference.
Notwithstanding known meticulous procedures to obtain and use autograft material from a patient during a surgical procedure, there is no guarantee that a reliable and strong fusion will ultimately result, and that a so-called “non-union” will be avoided. A need therefore exists for a system and procedure for obtaining and depositing autograft material between two vertebrae to be fused so that the material spans the intervertebral disc space, enters the vertebral bodies, and grows rapidly to produce a healthy, strong, and permanent fusion.